AFM Cantilever with in Situ Renewable Mercury Microelectrode

Abstract

We report here first results obtained on a novel, in situ renewable mercury microelectrode integrated into an atomic force microscopy (AFM) cantilever. Our approach is based on a fountain pen probe with appropriate dimensions enabling reversible filling with (nonwetting) mercury under changing the applied pressure at a connected mercury supply in a dedicated experimental setup. The fountain pen probe utilizes a special design with vertical pillars inside the channel to minimize mechanical perturbation. In proof of principle experiments, dropping and hanging mercury drop were observed as a function of the applied pressure at the external mercury supply. Electrical conductivity occurred only through the mercury after filling, and the empty fountain pen probe showed excellent electrical insulation. This was demonstrated by chronoamperometric measurements in the electrolyte and by mechanical and electrical contacting of an ITO substrate with a mercury-filled and empty probe in air. Finally, cyclic voltammetry and square wave voltammetry were done in a static mercury electrode fountain pen configuration, demonstrating the principle usability of the mercury probe for electrochemical studies. Our findings are of fundamental importance as they enable further integration of a renewable mercury electrode probe into an AFM setup, which is the subject of ongoing work.

Extending applications of AFM to fluidic AFM in single living cell and extracellular vesicle studies

“…A hollow silicon nitride (Si3N4) tip on a silicon dioxide (SiO2) fluidic cantilever and an array of these devices was developed for high throughput applications 73 . A silicon nitride fluidic cantilever without a tip was reported by Schön et al 74 and in a later effort, a tip with a submicron aperture was included 75 . Other efforts included the use of flexible materials like SU-8 as a cantilever material 70,[76][77][78] .…”

Volume and concentration dosing in picolitres using a two-channel microfluidic AFM cantilever

“…The probes were made from silicon-rich silicon nitride by a process described elsewhere. 29,30 The microchannels were prepared by the removal of an encapsulated sacrificial polycrystalline silicon layer. To obtain a proper separation of the fluidic channels in the pyramidal tip and to merge these channels together at the tip apex, a rather complex processing based on corner lithography was used.…”

Functionalization of Scanning Probe Tips with Epitaxial Semiconductor Layers

“…Following this path, these well‐established analytical methods could then be brought to the nanoscale for routine analyses of nanomaterials. In this context, different advanced strategies for tip functionalization have been adopted and they can be coarsely divided into: i) coating of the surface of existing tips with metals, dielectrics, molecules, nanocrystals, or quantum dots; ii) attachment of pre‐existing functional nano‐objects such as metal nanowires, carbon nanotubes, or fluorescent particles; iii) nanofabrication of structures on the tip itself, including fluidic channels for liquid electrodes, optical nanoantennas for spectroscopy, and electrical contacts . The direct fabrication of scanning probe tips out of functional bulk materials different from inert silicon or glass has seldom been reported, although this strategy would clearly provide the advantage of a probe with precisely precharacterized material properties.…”